Compounds of formula VII have been disclosed to be potent inhibitors of HCV protease useful in treatment on patients infected with HCV. A particularly useful intermediate is a
compound of formula VIII. Dienes of formula I wherein R1 is an amino protecting group and X is a halogen atom are useful intermediates for the manufacture of macrocyclic HCV protease inhibitors of the formula VII and VIII.
The known processes for the preparation of the diene compound of the formula I suffer from unstable intermediates, lack of purification steps, the use of corrosive reagents and intermediates, and hazardous and expensive coupling reagents (PCT Publication WO 2005/037214). Therefore the known process is not suitable for large scale production.